申論題

5.You are going to carry out an experiment to determine whether surface finish has an effect on the endurance limit of steel. It is expected that polishing increases the average endurance limit. In such an experiment, you want to detect that polishing fails to have an effect with a probability of 0.99 (i.(E), a = 0.01) and you also want to detect a change in the average endurance limit of 700 units by a probability of at least 0.9. If it is known that the standard deviation of the endurance limit of the steel is 420 units, then the sample size that would be needed to perform this experiment is____________ . Assume that for a = 0.01, Za = 2.5 and forβ -0.10, 2β- 1.5.